Method for isomerizing 2-methyl-1-butene

Abstract

The invention discloses a method for isomerizing 2-methyl-1-butene, which adopts crude isopentene as a raw material and comprises the following steps: firstly, carrying out hydration reaction on part of crude isopentene through a catalyst bed layer to generate a reaction mixture containing tert-amyl alcohol; reacting the reaction mixture with the rest of crude isopentene in an isomerization reactor to obtain an isopentene primary product; and rectifying to obtain a high-purity isoamylene product and a high-purity tert-amyl alcohol product at the same time.

Description

Technical Field

[0001] The invention relates to the field of chemical materials, and in particular to a method for isomerizing 2-methyl-1-butene to 2-methyl-2-butene. Background Art

[0002] Isoamylene is an important chemical raw material and can be used to produce pinacolone, tert-amylbenzene, isoprene, etc.

[0003] Isoamylene is usually a mixture of 2-methyl-2-butene and 2-methyl-1-butene, and the content of 2-methyl-2-butene determines the value of the isoamylene product.

[0004] Isoamylene mainly exists in the C5 fraction of catalytic cracking gasoline or the C5 fraction produced as a byproduct of naphtha cracking to produce ethylene. Since these C5 materials contain many compounds with very close boiling points, it is not easy to separate isoamylene from them. The most commonly used separation method is the methyl tert-amyl ether cracking method, that is, the C5 fraction reacts with methanol to produce methyl tert-amyl ether, which is then refined to obtain high-purity methyl tert-amyl ether, and then cracked at high temperature to obtain isoamylene.

[0005] The C5 separation unit uses crude isopentene and methanol as by-products as raw materials. The crude isopentene and methanol are subjected to etherification reaction to produce high-purity tert-amyl methyl ether, and then tert-amyl methyl ether is decomposed to obtain high-purity isopentene. After an isomerization process, 2-methyl-butene-1 (2MB1) is isomerized to 2-methyl-butene-2 ​​(2MB2), thereby obtaining an isopentene product with a high 2MB2 content.

[0006] In the isomerization catalytic reaction, the dimerization of isopentene is the most important side reaction, which not only reduces the yield of the target product, but more importantly, the heat of the dimerization reaction can easily increase the catalyst bed temperature, thereby initiating the dimerization of 2M2B, further reducing the selectivity of the reaction and shortening the service life of the resin catalyst.

[0007] While the isomerization reaction is being carried out, 2-methyl-2-butene and 2-methyl-1-butene are easily dimerized individually or mutually. Chinese patent CN101597201A adds tert-amyl alcohol to crude isopentene, and then passes it through a fixed bed catalyst bed composed of a sulfonic acid cation exchange resin to carry out an isomerization reaction, so that 2-methyl-1-butene in the crude isopentene is converted into 2-methyl-2-butene. The key to this invention is that an appropriate amount of tert-amyl alcohol is added before the isomerization raw material passes through the catalyst bed to inhibit dimerization during the isomerization reaction.

[0008] Chinese patent CN101723787A adds water to the raw material isopentene, and then passes it through a fixed bed catalyst bed composed of sulfonic acid cation exchange resin to perform an isomerization reaction, so that 2-methyl-1-butene in the raw material isopentene is converted into 2-methyl-2-butene. The key to this invention is that an appropriate amount of water is added before the raw material of the isomerization reaction passes through the catalyst bed, which inhibits the dimerization reaction and reduces the content of dimers in the isomerization reaction product to less than 1%.

[0009] In the prior art, water or tert-amyl alcohol is directly added to the isomerization raw material, which reduces the dimerization reaction, but also has certain disadvantages. The added water is easily brought into the product, affecting the separation operation and product quality. The addition of purchased tert-amyl alcohol is easy to bring in new impurities and increase production costs. Summary of the invention

[0010] In view of the shortcomings of the prior art in which water or tert-amyl alcohol is directly added to the isomerization raw material to reduce the dimerization reaction and promote the conversion of 2-methyl-1-butene into 2-methyl-2-butene, the object of the present invention is to provide a combined process for isopentene isomerization: the present invention first utilizes part of the crude isopentene raw material for hydration reaction, and then enters the isomerization reactor together with the remaining isopentene for reaction, and then the reaction product is separated by a distillation tower, so as to produce a high-value and high-purity isopentene product with a high 2-methyl-2-butene content in the side line.

[0011] The present invention provides a method for isomerizing 2-methyl-1-butene, comprising the following steps:

[0012] S1: using crude isopentene as a raw material, fully mixing part of the crude isopentene with water, and performing a hydration reaction through a catalyst bed to generate a reaction mixture containing tert-amyl alcohol; wherein the amount of the part of the crude isopentene is 2% to 30% of the total mass of the raw crude isopentene; the tert-amyl alcohol has the effect of inhibiting the activity of the isomerization catalyst, reducing the occurrence of isopentene dimerization, and increasing the proportion of 2-methyl-2-butene in the system;

[0013] S2: the reaction mixture obtained in step S1 and the remaining crude isopentene are introduced into an isomerization reactor to react under the action of a catalyst to obtain an isopentene primary product; wherein the amount of the remaining crude isopentene is 98% to 70% of the total mass of the raw crude isopentene;

[0014] S3: The primary isopentene product obtained in step S2 is distilled in a distillation tower, tert-amyl alcohol and heavy component impurities are removed from the bottom of the distillation tower, and the isopentene product is obtained by side-line extraction.

[0015] Preferably, in step S1, the water-olefin molar ratio is 1:(20-2), the catalyst is a sulfonic acid cation exchange resin, the mass exchange capacity is 3.0-6.0 mmol / g, and the liquid hourly volume space velocity is 0.01-1 hr -1 , the reaction temperature is 20-80°C, and the reaction pressure is 0.1-3.0MPa.

[0016] Preferably, in step S2, the catalyst is a sulfonic acid cation exchange resin with a mass exchange capacity of 3.0 to 6.0 mmol / g and a liquid hourly volume space velocity of 0.5 to 10 hr -1 , the reaction temperature is 20-50°C, and the reaction pressure is 0.1-1.0MPa.

[0017] Preferably, in step S3, the bottom temperature of the distillation tower is 69-167° C., the top temperature is 18-92° C., the reflux ratio is 10-40; and the top pressure is 0.05-0.5 MPa.

[0018] Preferably, in step S1 or S2, the catalyst is a macroporous sulfonic acid cation exchange resin with a pore size of ≥20 nm. Macroporous resin is a porous sponge-like structure skeleton with a large number of permanent micropores inside, a large specific surface area, many active centers, fast ion diffusion rate, and fast ion exchange rate. Macroporous resin is resistant to swelling, not easy to break, wear-resistant, heat-resistant and temperature-resistant, easy to adsorb and exchange organic macromolecules, and has strong anti-pollution ability.

[0019] More preferably, in step S1, the water-olefin molar ratio is 1:(15-8), the mass exchange capacity of the macroporous sulfonic acid cation exchange resin is 4.0-5.5 mmol / g, and the liquid hourly volume space velocity is 0.05-0.5 hr -1 , the reaction temperature is 50-70°C, and the reaction pressure is 0.5-2.4MPa.

[0020] More preferably, in step S2, the mass exchange capacity of the macroporous sulfonic acid cation exchange resin is 4.0 to 5.5 mmol / g, and the liquid hourly volume space velocity is 3 to 6 hr -1 , the reaction temperature is 25-35°C, and the reaction pressure is 0.3-0.8MPa.

[0021] More preferably, in step S3, the bottom temperature of the distillation tower is 99-142° C., the top temperature is 35-72° C., the reflux ratio is 20-30, and the top pressure is 0.1-0.3 MPa.

[0022] The method further comprises step S4: further distilling and separating the tert-amyl alcohol product removed from the bottom of the tower in step S3, and extracting the tert-amyl alcohol product from the side line.

[0023] Preferably, in step S4, the bottom temperature of the distillation tower is 125-233° C., the top temperature is 49-137° C., the reflux ratio is 20-80; and the top pressure is 0.03-0.4 MPa.

[0024] More preferably, in step S4, the bottom temperature of the distillation tower is 134-196° C., the top temperature is 59-105° C., the reflux ratio is 30-50; and the top pressure is 0.05-0.2 MPa.

[0025] By adopting the method provided by the invention, the purity of the obtained isopentene product is greater than 99%, and the content ratio of 2-methyl-2-butene to 2-methyl-1-butene is greater than 10; the purity of the obtained tert-amyl alcohol product is greater than 95%.

[0026] In the present invention, after a part of the isopentene raw material (2%-30% of the total mass of the raw material crude isopentene) is reacted with water in step S1, the product does not need to be separated, and directly enters the isomerization reactor together with the remaining isopentene for isomerization reaction in step S2. Since a small amount of tert-amyl alcohol is generated during the hydration reaction of S1, the dimerization of isopentene in the isomerization process can be well suppressed; at the same time, the reaction activity of 2-methyl-1-butene is higher than that of 2-methyl-2-butene, and its conversion rate is also higher, and the proportion of 2-methyl-2-butene in the hydration reaction system is correspondingly increased.

[0027] At the same time, the inventors have also found through experiments that the hydration reaction can use the same sulfonic acid group cation exchange resin as the isomerization reaction, and large-particle macroporous styrene divinylbenzene cation exchange resin is particularly preferred. By controlling different process conditions and optimizing the isomerization process, a high-purity and high-value isopentene product can be obtained to meet the product market requirements.

[0028] Compared with the prior art, the technical effects of the present invention are as follows:

[0029] (1) Impurities that may be introduced by adding water or tert-amyl alcohol are effectively avoided. At the same time, the water content in the reaction system is lower, which is more conducive to separation operation and improves product quality.

[0030] (2) There is no need to purchase tert-amyl alcohol from outside, which reduces dependence on external supply and reduces production costs.

[0031] (3) Through the ingenious design, effective combination and adjustment optimization of experimental ideas and process flow, tert-amyl alcohol was self-generated through experiments. At the same time, macroporous sulfonic acid cation exchange resin was used as a catalyst, and the process parameters were selected. While improving production efficiency, high-purity (greater than 99%) and high-value (high 2-methyl-2-butene content) isopentene products were obtained, which improved the competitiveness of the technical route.

[0032] (4) In addition, through further optimization of the process flow, high-purity tert-amyl alcohol products can also be obtained at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The isopentene isomerization process and tert-amyl alcohol separation process flow chart provided by the embodiment of the present invention. Explanation of the reference numerals: 100: hydration reactor, 200: isomerization reactor, 300: isopentene distillation column, 400: tert-amyl alcohol distillation column, W1: reaction mixture containing tert-amyl alcohol, W2: primary isopentene product, W3: high-purity isopentene product, W4: high-purity tert-amyl alcohol product. DETAILED DESCRIPTION

[0034] The following specific embodiments provide exemplary explanations of the present invention and help further understand the present invention, but the specific details of the implementation cases are only for illustrating the present invention and do not represent all the technical solutions under the concept of the present invention. Therefore, they should not be understood as limiting the overall technical solution of the present invention. Some non-substantial additions and modifications that do not deviate from the concept of the present invention in the opinion of technical personnel, such as simple replacement or substitution of technical features with the same or similar technical effects, all fall within the scope of protection of the present invention.

[0035] Example 1

[0036] The process flow of the embodiment is as follows Figure 1 As shown:

[0037] S1: Using crude isopentene as raw material, part of the crude isopentene is fully mixed with water, and then enters the hydration reactor 100, and undergoes hydration reaction through the catalyst bed to generate a reaction mixture W1 containing tert-amyl alcohol; wherein the amount of the part of the crude isopentene is 2% of the total mass of the raw crude isopentene; the water-olefin molar ratio is 1:20, and the catalyst is a macroporous sulfonic acid-based cation exchange resin with a pore size of ≥20 nm, a mass exchange capacity of 3.0 mmol / g, and a volume space velocity of 0 liquid hour of 0.01 hr -1 , the reaction temperature is 20°C and the reaction pressure is 0.1MPa.

[0038] S2: The reaction mixture W1 obtained in step S1 and the remaining crude isopentene are introduced into an isomerization reactor 200 to react under the action of a catalyst to obtain an isopentene primary product W2; wherein the amount of the remaining crude isopentene is 98% of the total mass of the raw crude isopentene; the catalyst is a macroporous sulfonic acid-based cation exchange resin with a pore size of ≥20 nm, a mass exchange capacity of 3.0 mmol / g, and a liquid hourly volume space velocity of 0.5 hr -1 , the reaction temperature is 20°C and the reaction pressure is 0.1MPa.

[0039] S3: The isopentene primary product W2 obtained in step S2 is distilled in a distillation tower 300, tert-amyl alcohol and heavy impurities are removed from the bottom of the distillation tower, and the isopentene product W3 is obtained by side-line extraction; the bottom temperature of the distillation tower is 69° C., the top temperature is 18° C., the reflux ratio is 10; and the top pressure is 0.05 MPa.

[0040] S4: The tert-amyl alcohol product removed from the bottom of the tower in step S3 is further distilled and separated by a distillation tower 400, and the tert-amyl alcohol product W4 is obtained by side-line extraction. The bottom temperature of the distillation tower is 125°C, the top temperature is 49°C, the reflux ratio is 20, and the top pressure is 0.03Pa.

[0041] Embodiments 2 to 6

[0042] The steps of Examples 2 to 6 are basically the same as those of Example 1, but the specific parameter values ​​are different. The specific experimental parameters are shown in Table 1.

[0043] The performance parameters of the products obtained in Examples 1 to 6 are shown in Table 1.

[0044] Table 1 Parameter values ​​and product performance of the examples

[0045]

[0046]

[0047] In summary, it can be seen from Table 1 that by adopting the method provided by the present invention, after hydration, isomerization and distillation steps, the purity of the obtained isopentene is above 99%, and the content ratio of 2-methyl-2-butene to 2-methyl-1-butene is greater than 10. At the same time, the purity of the obtained tert-amyl alcohol product is also above 95%. By adopting the method provided by the present invention, the cost is reduced, the impurities are reduced, good technical effects are achieved, and a high-purity and high-value isopentene product is obtained, which can meet the market requirements; at the same time, a high-purity tert-amyl alcohol product is also obtained.

[0048] The above description is only a preferred embodiment of the present invention and does not limit it. Although the present patent is described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions recorded in the aforementioned embodiments or to replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention are included in the protection scope of the present invention.

Claims

1. A method for isomerizing 2-methyl-1-butene, characterized in that: The following steps are involved: S1: using crude isopentene as a raw material, fully mixing part of the crude isopentene with water, and performing a hydration reaction through a catalyst bed to generate a reaction mixture containing tert-amyl alcohol; wherein the amount of the part of the crude isopentene is 2% to 30% of the total mass of the raw crude isopentene; S2: the reaction mixture obtained in step S1 and the remaining crude isopentene are introduced into an isomerization reactor to react under the action of a catalyst to obtain an isopentene primary product; wherein the amount of the remaining crude isopentene is 98% to 70% of the total mass of the raw crude isopentene; S3: The primary isopentene product obtained in step S2 is distilled in a distillation tower, tert-amyl alcohol and heavy component impurities are removed from the bottom of the distillation tower, and the isopentene product is obtained by side-line extraction.

2. The method for isomerization of 2-methyl-1-butene according to claim 1, characterized in that: In step S1, the water-olefin molar ratio is 1:(20-2), the catalyst is a sulfonic acid cation exchange resin, the mass exchange capacity is 3.0-6.0 mmol / g, and the liquid hourly volume space velocity is 0.01-1 hr -1 , the reaction temperature is 20-80°C, and the reaction pressure is 0.1-3.0MPa.

3. The method for isomerization of 2-methyl-1-butene according to claim 1, characterized in that: In step S2, the catalyst is a sulfonic acid cation exchange resin with a mass exchange capacity of 3.0 to 6.0 mmol / g and a liquid hourly volume space velocity of 0.5 to 10 hr -1 , the reaction temperature is 20-50°C, and the reaction pressure is 0.1-1.0MPa.

4. The method for isomerization of 2-methyl-1-butene according to claim 1, characterized in that: In step S3, the bottom temperature of the distillation tower is 69-167° C., the top temperature is 18-92° C., the reflux ratio is 10-40; and the top pressure is 0.05-0.5 MPa.

5. The method for isomerization of 2-methyl-1-butene according to claim 1, characterized in that: In step S1 or S2, the catalyst is a macroporous sulfonic acid cation exchange resin with a pore size of ≥20 nm.

6. A method for isomerizing 2-methyl-1-butene as claimed in claim 1 or 5, characterized in that: In step S1, the water-olefin molar ratio is 1:(15-8), the mass exchange capacity of the macroporous sulfonic acid cation exchange resin is 4.0-5.5 mmol / g, and the liquid hourly volume space velocity is 0.05-0.5 hr -1 , the reaction temperature is 50-70°C, and the reaction pressure is 0.5-2.4MPa.

7. A method for isomerizing 2-methyl-1-butene as claimed in claim 1 or 5, characterized in that: In step S2, the mass exchange capacity of the macroporous sulfonic acid cation exchange resin is 4.0-5.5 mmol / g, and the liquid hourly volume space velocity is 3-6 hr -1 , the reaction temperature is 25-35°C, and the reaction pressure is 0.3-0.8MPa.

8. The method for isomerization of 2-methyl-1-butene according to claim 1, characterized in that: In step S3, the bottom temperature of the distillation tower is 99-142° C., the top temperature is 35-72° C., the reflux ratio is 20-30, and the top pressure is 0.1-0.3 MPa.

9. The method for isomerizing 2-methyl-1-butene according to claim 1, characterized in that: The method further comprises step S4: further distilling and separating the tert-amyl alcohol product removed from the bottom of the tower in step S3, and extracting the tert-amyl alcohol product from the side line.

10. A method for isomerizing 2-methyl-1-butene as claimed in claim 1 or 10, characterized in that: In step S4, the bottom temperature of the distillation tower is 125-233° C., the top temperature is 49-137° C., the reflux ratio is 20-80, and the top pressure is 0.03-0.4 MPa.

11. A method for isomerizing 2-methyl-1-butene as claimed in claim 1 or 11, characterized in that: In step S4, the bottom temperature of the distillation tower is 134-196° C., the top temperature is 59-105° C., the reflux ratio is 30-50, and the top pressure is 0.05-0.2 MPa.

12. The method for isomerizing 2-methyl-1-butene according to claim 1, characterized in that: The obtained isopentene product has a purity greater than 99%, and a content ratio of 2-methyl-2-butene to 2-methyl-1-butene greater than 10.

13. The method for isomerizing 2-methyl-1-butene according to claim 1, characterized in that: The purity of the obtained tert-amyl alcohol product is greater than 95%.

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